Re: Maplin Z80 SBC
The titchy little MAX232 PCBs without connector are only about £2+.
You need not modify or replace the existing RS232 receive level converter, just break the connection between the RS232 input pin on the socket and the input of the original (unmodified) receive level converter and insert the circuit below.
It will beef up the weedy RS232 being generated by your USB-serial lead and convert it into a full-fat RS232 signal which the input of the original level-converter will then deem acceptable.
This assumes that you are not using hardware handshaking, if you are then you would also have to break and buffer any handshaking input signals as well, using further pairs of MAX232 elements.
If you were feeling exceptionally adventurous you could (carefully) hack the 9-way moulded plug on the end of the USB-serial lead to pieces, swap a solderable plug and removable long-bodied plug housing onto the end of the cable and put the mini MAX232 buffer in there, because there will already be +5V available inside that D-plug to power whatever is originally in there.
|